Fix a Backpack recompilation avoidance bug when signatures change.

Summary:
Recompilation avoidance checks if -this-unit-id has changed by relying
on the "wanted module" check in readIface ("Something is amiss...").
Unfortunately, this check didn't check if the instantiation made
sense, which meant that if you changed the signatures of a Backpack
package, we'd still treat the old signatures as up-to-date.

The way I fixed this was by having findAndReadIface take in a 'Module'
representing the /actual/ module we were intending to lookup.  We
convert this into the 'Module' we expect to see in 'mi_module' and
now do a more elaborate check that will also verify that instantiations
make sense.

Along the way, I robustified the logging infrastructure for
recompilation checking, and folded wrongIfaceModErr (which
was dead code) into the error message.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: bgamari, austin

Subscribers: thomie, snowleopard

Differential Revision: https://phabricator.haskell.org/D3130

10 files changed, 84 insertions, 1 deletions

diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/.gitignore b/testsuite/tests/backpack/cabal/bkpcabal04/.gitignore
new file mode 100644
index 0000000000..4a6a47f966
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/.gitignore
@@ -0,0 +1,3 @@
+bkpcabal04.cabal
+q/B.hsig
+q/A/B.hsig
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/Makefile b/testsuite/tests/backpack/cabal/bkpcabal04/Makefile
new file mode 100644
index 0000000000..0e81107d9e
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/Makefile
@@ -0,0 +1,29 @@
+TOP=../../../..
+include $(TOP)/mk/boilerplate.mk
+include $(TOP)/mk/test.mk
+
+SETUP='$(PWD)/Setup' -v0
+CONFIGURE=$(SETUP) configure $(CABAL_MINIMAL_BUILD) --with-ghc='$(TEST_HC)' --ghc-options='$(TEST_HC_OPTS)' --package-db='$(PWD)/tmp.d' --prefix='$(PWD)/inst'
+
+bkpcabal04: clean
+	$(MAKE) -s --no-print-directory clean
+	'$(GHC_PKG)' init tmp.d
+	'$(TEST_HC)' -v0 --make Setup
+	cp bkpcabal04.cabal.in1 bkpcabal04.cabal
+	cp q/B.hsig.in q/B.hsig
+	# typecheck
+	$(CONFIGURE)
+	$(SETUP) build
+	# new version
+	cp bkpcabal04.cabal.in2 bkpcabal04.cabal
+	rm q/B.hsig
+	cp q/A/B.hsig.in q/A/B.hsig
+	# typecheck
+	$(CONFIGURE)
+	$(SETUP) build
+ifneq "$(CLEANUP)" ""
+	$(MAKE) -s --no-print-directory clean
+endif
+
+clean :
+	$(RM) -rf tmp.d inst dist Setup$(exeext) q/A/B.hsig q/B.hsig bkpcabal04.cabal
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/Setup.hs b/testsuite/tests/backpack/cabal/bkpcabal04/Setup.hs
new file mode 100644
index 0000000000..9a994af677
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/all.T b/testsuite/tests/backpack/cabal/bkpcabal04/all.T
new file mode 100644
index 0000000000..998882ef5e
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/all.T
@@ -0,0 +1,10 @@
+if config.cleanup:
+   cleanup = 'CLEANUP=1'
+else:
+   cleanup = 'CLEANUP=0'
+
+# Test recompilation checking on signatures
+test('bkpcabal04',
+     normal,
+     run_command,
+     ['$MAKE -s --no-print-directory bkpcabal04 ' + cleanup])
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in1 b/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in1
new file mode 100644
index 0000000000..1ce11c5bcc
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in1
@@ -0,0 +1,17 @@
+name:                bkpcabal04
+version:             0.1.0.0
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          ezyang@cs.stanford.edu
+build-type:          Simple
+cabal-version:       >=1.25
+
+library p
+  signatures: A
+  build-depends: base
+  hs-source-dirs: p
+
+library q
+  signatures: B
+  build-depends: base, p
+  hs-source-dirs: q
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in2 b/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in2
new file mode 100644
index 0000000000..e6fa4c6660
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/bkpcabal04.cabal.in2
@@ -0,0 +1,17 @@
+name:                bkpcabal04
+version:             0.1.0.0
+license:             BSD3
+author:              Edward Z. Yang
+maintainer:          ezyang@cs.stanford.edu
+build-type:          Simple
+cabal-version:       >=1.25
+
+library p
+  signatures: A
+  build-depends: base
+  hs-source-dirs: p
+
+library q
+  signatures: A.B
+  build-depends: base, p
+  hs-source-dirs: q
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/p/A.hsig b/testsuite/tests/backpack/cabal/bkpcabal04/p/A.hsig
new file mode 100644
index 0000000000..cd83bfff2a
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/p/A.hsig
@@ -0,0 +1 @@
+signature A where
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/q/A/B.hsig.in b/testsuite/tests/backpack/cabal/bkpcabal04/q/A/B.hsig.in
new file mode 100644
index 0000000000..797f45c401
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/q/A/B.hsig.in
@@ -0,0 +1,2 @@
+signature A.B where
+import A
diff --git a/testsuite/tests/backpack/cabal/bkpcabal04/q/B.hsig.in b/testsuite/tests/backpack/cabal/bkpcabal04/q/B.hsig.in
new file mode 100644
index 0000000000..30fdf7e274
--- /dev/null
+++ b/testsuite/tests/backpack/cabal/bkpcabal04/q/B.hsig.in
@@ -0,0 +1,2 @@
+signature B where
+import A
diff --git a/testsuite/tests/backpack/should_compile/bkp51.bkp b/testsuite/tests/backpack/should_compile/bkp51.bkp
index af0a422464..6b8cecbc64 100644
--- a/testsuite/tests/backpack/should_compile/bkp51.bkp
+++ b/testsuite/tests/backpack/should_compile/bkp51.bkp
@@ -24,7 +24,7 @@ unit s where
         import D
         z = show id
 unit t where
-    dependency r[B=s:E,H=<H>]
+    dependency r[B=s[H=<H>]:E,H=<H>]
     module F where
         import D
         a = show id